Developer liquid supplying method and device for liquid development electrophotography

ABSTRACT

A developer liquid supplying method and a device therefor wherein a developer liquid prepared in advance at a certain concentration level required to keep the concentration of the developer liquid in the developer liquid tank at a fixed level is supplied automatically only when the developer liquid in the developer liquid tank decreases and otherwise the developer liquid for supply is intercepted from the developer liquid in the developer liquid tank.

United States Patent [191 Suzuki et 8L 1 51 Feb. 27, 1973 [54] DEVELOPER LIQUID SUPPLYING METHOD AND DEVICE FOR LIQUID DEVELOPMENT ELECTROPHOTOGRAPHY Inventors: Shigeru Suzuki, Yokohama; Tadaaki Kanno, Tokyo; Tadatoshi Sakamaki, Kawasaki, all of Japan Kabushiki Kaisha Ricoh, Tokyo, Japan Filed: Nov. 14, 1969 Appl. No.: 876,846

[73] Assignee:

[30] Foreign Application Priority Data Dec. 27, 1968 Japan ..43/370 US. Cl. ..137/433, 137/572, 95/89 Int. Cl. ..G03d 3/00 Field of Search ..95/89; 355/10; 25 l/l49.7;

[56] References Cited UNITED STATES PATENTS 2,063,140 12/1936 Allison ..137/572X 1,922,117 8/1933 Turner ..137/572 X 2,915,325 12/1959 Foster ..251/149.7 X 3,189,063 6/1965 Lowe ..137/433 X 3,260,185 7/1966 Limberger ..95/89 3,368,525 2/1968 Sacre ..95/89 X Primary Examiner-Alan Cohan Attorney-Emest G. Montague [5 7] ABSTRACT 1 Claim, 2 Drawing Figures 4:11:11: Ill!!! IIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIII 'KiwL- ATTO R N EY DEVELOPER LIQUID SUPPLYING METHOD AND DEVICE FOR LIQUID DEVELOPMENT ELECTROPIIOTOGRAPHY This invention relates to a developer liquid supplying method and a device therefor to be used in liquid development electrophotography.

Developer liquid for liquid development electrophotography is made by dispersing in an electrically high resistive solution the so-called toner comprising finely divided particles of carbon black, et al. coated with resin films. Only when the concentration of the toner in the above-mentioned developer liquid is kept at a required level, photosensitive paper bearing an electrostatic latent image can be developed in a good condition.

Now, when development is repeated several times in a developing tank filled with the above-mentioned developer liquid, the developer liquid and the toner are adhered to photosensitive paper and are consumed, so that the quantity of the developer liquid and the toner density gradually decrease. Therefore, the quantity of the developer liquid'and the toner density should be kept constant by continual supply of new developer liquid and toner.

Hitherto, the following methods have been used to supply developer liquid or toner in order to keep the quantity of the developer liquid or the toner density constant.

1. Visual Method A developer liquid is caused to pass through a transparent slit, and light is transmitted through it. Judging the darkness by view, developer liquid or toner is supplied'manually. According to this method, the toner in the developer liquid adheres to the transparent wall of the slit, and hinders accurate judgement. Further, as the density is judged by the naked eye, it is accompanied by individual variations and accurate judgement cannot be expected. What is still worse is that the effect of the manual supply does not appear soon at the transparent slit part, but appears after a certain delay time, fine adjustment is very difficult, and the minute control of the manual supply is not so easy.

2. Electrical Control Method Using a Photocell A transmitted light through a developer liquid in the transparent slit part is detected by a photocell, and a valve is opened or closed in accordance with the photoelectromotive force from the photocell to supply a developer liquid or a toner. The mechanism forthis' method is extremely complex and expensive. Moreover, it is feared that the toner will adhere to the wall of the transparent slit and that the photocell will not work well.

3. Method wherein a certain amount of concentrated toner solution is supplied whenever a fixed number of sheets of paper are developed:

The consumption of a developer liquid or a toner depends on the size of photosensitive paper and on the density of an image on the original, and it is difficult to keep the concentration of the developer liquid at a required concentration level.

In order to supply the developer liquid tank with a developer liquid for supply prepared in advance in accordance with the decrease of the developer liquid in the developer liquid tank, a valve for automatically supplying the developer liquid to a constant liquid surface height (for example, a valve 21 as shown in FIG. 2) is usually used, but though it is convenient to supply the developer liquid for supply automatically in accordance with the decrease of developer liquid in the developer liquid tank, yet the valve mentioned above is almost always open, and the developer liquid for supply is not intercepted from the developer liquid in the developer liquid tank, so that the toner in the developer liquid for supply flows down and precipitates in a long time and moves into the developer liquid tank. Therefore, the concentration of the developer liquid for supply decreases and the required concentration cannot be maintained.

Although the toner in the developer liquid for liquid development electrophotography comprises extremely finely divided particles, it has a tendency to precipitate in a long time, and it is necessary to separate the developer liquid for supply from the developer liquid in the developer liquid tank, except when the developer liquid for supply is supplied in order to keep the concentration of the developer liquid at a certain level. The characteristic feature of the present invention also consists in solving the problem like this.

It is an object of the present invention to overcome all the defects seen in the conventional methods.

It is another'object of the present invention to provide a developer liquid supplying method and a device therefor wherein a developer liquid prepared in advance at a certain concentration level required to keep the concentration of the developer liquid in the developer liquid tank at a fixed level is supplied automatically only when the developer liquid in the developer liquid tank decreases and otherwise the developer liquid for supply is intercepted from the developer liquid in the developer liquid tank.

We, the inventors, have found the following relationship experimentally;

wherein, D [g/I] is a required concentration of developer liquid in the developer liquid tank, D [g/l] is a concentration of developer liquid after 11 sheets of photosensitive paper have been developed, D, [g/l] is a concentration of developer liquid for supply, V [l] is a fixed quantity of developer liquid in the developer liquid tank, and V, [l] is a quantity of the developer liquid required for the development of n sheets of photosensitive paper. D and V, seen in the above-mentioned equation can be determined experientially or statistically by judging the size and the letter density of an original to be copied, and D is determined from experiments. Since V is a value to be determined in design, D can be obtained automatically from the equation. And as the required concentration D itself has a certain amount of allowance experimentally, the concentration of developer liquid in the developer liquid tank can be kept at a certain fixed level, if V,, [l] of the developer liquid for supply with a concentration D, is supplied.

As described above, D, and V,, are determined experientially or statistically, and the size and the letter density, etc. of originals are almost constant for each company or office which uses the copying machine, so that if these values have a tendency to be quite different for each customer, D,, and V, may be determined in accordance with each particular situation, and be classified in several steps. Several kinds of developer liquids should be prepared in advance in such a case.

For a better understanding of the invention, reference is made to the following detailed disclosure of this invention taken in conjunction with the accompanying drawing wherein:

FIG. 1 is a schematic cross sectional view of a developing apparatus incorporating therein an example of the developer liquid supplying device according to the present invention; and

FIG. 2 is a cross sectional view of a developing apparatus incorporating therein another example of the developer liquid supplying device according to the invention.

In FIG. 1, a developer liquid tank 1 is filled with a developer liquid 2. A path 3 of photosensitive paper to be developed consists of a pair of photosensitive paper feed-in rollers 4, upper and lower photosensitive paper guide plates 5 for dipping photosensitive paper in the developer liquid 2 and a pair of photosensitive paper feed-out and squeezing rollers 6, etc. A developer liquid is housed in a developer liquid tank 7, whose concentration is adjusted at D, in advance in order to keep the concentration of the developer liquid 2 in the developer liquid tank 1 at a required level D. This tank 7 is connected with the developer liquid tank 1 through a pipe 8. To the pipe 8, a valve 9 is mounted having a movable valve 9a which can intercept the flow of the developer liquid for supply. At the right side of the developer liquid tank I seen in FIG. 1, a swinging member 11 at one end of which a float 10 is mounted is mounted for swing so as to float the above-mentioned float 10 in the developer liquid 2. The other end of the swinging member 11 corresponds to an actuator piece 12a of a normally opened microswitch 12. And the microswitch 12 works as a switch for an electromagnet 13 to drive the movable valve 9a of the valve 9. If the developer liquid decreases in the course of development of photosensitive paper, the float 10 goes down in accordance with the descent of the surface of the liquid and rotates the swinging member 11 counterclockwise in the figure. As a result, the swinging member 11 pushes up the actuator piece 12a of the microswitch 12 and closes the microswitch 12. When the microswitch 12 is closed, the electromagnet 13 is excited, and the movable valve 9a of the valve 9 is displaced so'that the path of the developer liquid for supply may be opened. Thus, the developer liquid for supply flows into the developer liquid tank 1. When the developer liquid in the developer liquid tank 1 increases to a predetermined level, the float 10, going up, causes the microswitch 12 to open. The electromagnet 13 stops working and the movable valve 9a returns to the original position by itself, intercepting the path of the flow of the developer liquid for supply. Therefore, the toner in the developer liquid for supply does never sink down into the developer liquid 2. The developer liquid 2 is thus replenished and its density is adjusted at a required level D. The precipitation of toner in the tank 7 can be prevented even when it is left unused for a while, if the tank 7 is agitated before it is used.

FIG. 2 denotes a developing apparatus with a device in accordance with the invention using a developer liquid supply tank 22 having a constant fluid surfacetype developer liquid supply valve 21. In FIG. 2, a developer liquid 24 is housed in a developer liquid tank 23. On stage portions 230 and 23b of the developer liquid tank 23, a plate 26 is fixed. A path of photosensitive paper 25 is formed by a guide plate 27 supported by the plate 26, another guide plate 28 placed above it, a pair of photosensitive paper feed-in rollers 29 and 30 pressing each other, and a pair of photosensitive paper feed-out and squeeze-out rollers 31 and 32. Photosensitive paper is inserted in the direction shown by an arrow a. Both of the guide plates 27 and 28 mentioned above have downward bends in order to dip photosensitive paper in the developer liquid 24, and consist of metal plates with a number of longitudinal slits 27a and 28a. Within the developer liquid tank 23, a developer liquid stirring frame 33 is mounted loosely at the lower end of a dependent arm 35a of a swinging member 35 which is loosely mounted at a side wall by an axis 34. An upper bent edge 35b of another arm of the swinging member 35 is always pressed by a spring 36 upon an eccentric cam 32a mounted coaxially with the roller 32, and is swinged by the eccentric cam 32a co-rotating with the roller 32, making the frame 33 to reciprocate right and left in the figure. The frame 33 thus agitates the developer liquid 24 by its swinging movement, prevents the precipitation of toner and supplies a fresh developer liquid to photosensitive paper.

-Above the guiding plate 28, an intermediate developer liquid tank 37 is arranged and the developer liquid supply tank 22 is placed further above it. The constant fluid surface-type automatic supply valve 21 of the developer liquid tank 22, in the situation shown in the figure, causes the apex of a valve rod 21b of a valve 21a to collide against the bottom of the intermediate developer liquid tank 37 and the valve 21a is pushed upward against a spring 210, so that a supply path of a developer liquid for supply 38 in the abovementioned tank 22 is always opened for the intermediate developer liquid tank 37. The tank 22 is, under the condition shown in the figure, elastically fixed by stoppers 41 and 42 fixed on elastic members 39 and 40. A pressing spring 44 of a cleaning apparatus with a felt 43 pressed against the roller 31 is fixed on the side of a supporting plate 48 of the tank 22, and the felt 31 is pressed upon the roller 31 by this spring 44.

One end of a pipe 45 is connected with an opening 37a of the intermediate developer liquid tank 37 mentioned above, and the other end of this pipe 45 is connected with a pipe 46b of a needle valve 46 which utilizes the buoyancy of a cork 46a. The valve 46 is fixed on the plate 26 with the upper part of the pipe 46b tightened by nuts 47. A penetrating hole 46b is drilled on the side wall of the pipe 46b and the bore of the part lower than the hole 46b is enlarged and a needle valve 46c is loosely coupled on it. The needle valve 460, fixed on a support member 46d together with a cork 46a, slides up and down along the enlarged part of the pipe 46b under the action of the cork 46a which is moved up and down in accordance with the up and down movement of the liquid surface, and moves its tip 460 back and forth with respect to the smaller radius part of the pipe 46b. Therefore, when the developer liquid 24 decreases, the cork 46a goes down, and the needle valve 460 leaves the smaller radius part of the pipe 46b.

As a result, the developer liquid for supply 38 in the intermediate developer liquid tank 37 flows down into the developer liquid tank 23. When the quantity of the developer liquid 24 reaches the predetermined level, the tip 46c of the above-mentioned needle valve 460, pushed up by the floating cork 46a, shuts down the smaller radius part of the pipe 46b, and the path for developer liquid supply is completely intercepted. Here, the upper end of the above-mentioned pipe 46b is opened at a height corresponding to the liquid surface when the valve 21 is just closed.

As described above, a constant fluid surface-type developer liquid supply valve 21 is always opened for the path of the developer liquid for supply in the state of supply, and the developer liquid for supply 38 in the tank 22 automatically flows down or stops flowing according to the up and down movement of the liquid surface of the developer liquid in the intermediate developer liquid tank 37. Therefore, in the case the above-mentioned tank 22 are directly connected with the developer liquid tank 23 through the valve 21, it is feared that the developer liquid 38 in the tank 22 will be opened to the developer liquid 24 in the developer liquid tank 23 and the toner in the developer liquid 38 will precipitate and flow into the developer liquid 24 in a long time. On the other hand, in an example in accordance with the present invention, the developer liquid tank 23 and the intermediate developer liquid tank 37 are isolated with each other by the needle valve 46 except when the developer liquid is supplied, and the problem mentioned above never happens in the present invention. Since the concentration of the developer liquid 38 is fixed at a value of D, in which the concentration of the developer liquid 24 can be kept at a value of D, the developer liquid 24 can be maintained at an optimum condition.

The apparatus according to the present invention as shown in FIGS. 1 and 2 can be properly modified so long as the modification does not depart from the principle of the present invention, and any means can be adopted to supply a developer liquid for supply automatically and to intercept the flow of developer liquid except when it is supplied.

in the present invention, no special concentration detector is used, and by simply supplying the developer liquid in according with the used quantity of the developer liquid, the concentration of developer liquid in the developer liquid tank can be maintained at a required level. Furthermore, the change of concentration owing to the precipitation of toner is prevented and the concentration of developer liquid can be maintained more accurately. The method and apparatus of the present invention are simple to make and easy to use, and the price of the copying machine can be kept down. Moreover, the present invention has an advantage that the apparatus is quite easy and convenient to handle.

What is claimed is:

l. A developer liquid supplying device in liquid development electrophotography comprising a developer liquid tank,

a tank for supplying developer liquid to house a developer liquid for supply prepared in advance of a supply concentration Dp to maintain a predetermined fixed quantity V to have a predetermined fixed concentration D of a developer liquid in a developer liquid tank and at a required predetermined level corresponding to said predetermined fixed quantity V,

a developer liquid supplying path connecting said tank for supplying developer liquid to said developer liquid tank, a valve means for opening and closing said developer liquid supplying path by detecting the quantity of developer liquid in said developer liquid tank by which said valve means is opened only when the quantity of developer liquid decreases below said predetermined level, maintaining the concentration D of developer liquid in said developer liquid tank by replenishing a quantity Vn of the developer liquid from a supply concentration Dp in proportion to the decrease of a quantity Vn of the developer liquid, Vn being the quantity consumed by n copies out of the quantity V of the developer liquid of said predetermined fixed concentration D to constantly maintain said quantity V at saidpredetermined level, and restoring a concentration Dn of the developer liquid in the tank decreased through development to at least an initial concentration D by replenishing a developer liquid of said supply concentration Dp, the following formula being used as a criterion for calculating said concentration Dp:

where Dn is the density of the developer liquid after having developed n copies of photosensitive paper, and Dp D n,

an intermediate developer liquid tank disposed below said tank for supplying said developer liquid and above said developer liquid tank and disposed in said supplying path connecting said tank for supplying the developer liquid and said developer liquid tank and receiving developer liquid from said tank for supplying developer liquid, a constant fluid surface-type automatic valve disposed between said tank for supplying developer liquid and said developer liquid supply tank for communicating said tanks with each other and including a spring biased valve rod disposed against the bottom of said intermediate developer liquid tank and causing said automatic valve to open communication between said tanks, said bottom of said intermediate developer liquid tank is concavely shaped extending down toward the developer liquid in said developer liquid tank, said tank for supplying developer liquid has an opening in which said automatic valve is cooperatively disposed and which extends downwardly into said intermediate developer liquid tank, and said valve means constitutes a float operated needle valve disposed in said developer liquid tank, a plate, connected to said developer liquid tank adjacent the top thereof, at least one guide plate supported by said plate and 7 8 curving into said developer liquid and having lonsaid valve means further comprising a pipe having a gitudinal slots therein, longitudinal opening cooperating with said float said intermediate developer liquid tank being supoperated needle valve and secured to said plate,

ported and over one of said guide plates, a horizontally disposed pipe communicating said said tank for supplying developer liquid extending at intermediate f P l q i tank with said its bottom into said intermediate slmdmal p s m Sald p p developer liquid tank, 

1. A developer liquid supplying device in liquid development electrophotography comprising a developer liquid tank, a tank for supplying developer liquid to house a developer liquid for supply prepared in advance of a supply concentration Dp to maintain a predetermined fixed quantity V to have a predetermined fixed concentration D of a developer liquid in a developer liquid tank and at a required predetermined level corresponding to said predetermined fixed quantity V, a developer liquid supplying path connecting said tank for supplying developer liquid to said developer liquid tank, a valve means for opening and closing said developer liquid supplying path by detecting the quantity of developer liquid in said developer liquid tank by which said valve means is opened only when the quantity of developer liquid decreases below said predetermined level, maintaining the concentration D of developer liquid in said developer liquid tank by replenishing a quantity Vn of the developer liquid from a supply concentration Dp in proportion to the decrease of a quantity Vn of the developer liquid, Vn being the quantity consumed by n copies out of the quantity V of the developer liquid of said predetermined fixed concentration D to constantly maintain said quantity V at said predetermined level, and restoring a concentration Dn of the developer liquid in the tank decreased through development to at least an initial concentration D by replenishing a developer liquid of said supply concentration Dp, the following formula being used as a criterion for calculating said concentration Dp: where Dn is the density of the developer liquid after having developed n copies of photosensitive paper, and Dp>D>Dn, an intermediate developer liquid tank disposed below said tank for supplying said developer liquid and above said developer liquid tank and disposed in said supplying path connecting said tank for supplying the developEr liquid and said developer liquid tank and receiving developer liquid from said tank for supplying developer liquid, a constant fluid surface-type automatic valve disposed between said tank for supplying developer liquid and said developer liquid supply tank for communicating said tanks with each other and including a spring biased valve rod disposed against the bottom of said intermediate developer liquid tank and causing said automatic valve to open communication between said tanks, said bottom of said intermediate developer liquid tank is concavely shaped extending down toward the developer liquid in said developer liquid tank, said tank for supplying developer liquid has an opening in which said automatic valve is cooperatively disposed and which extends downwardly into said intermediate developer liquid tank, and said valve means constitutes a float operated needle valve disposed in said developer liquid tank, a plate, connected to said developer liquid tank adjacent the top thereof, at least one guide plate supported by said plate and curving into said developer liquid and having longitudinal slots therein, said intermediate developer liquid tank being supported over one of said guide plates, said tank for supplying developer liquid extending at its bottom into said intermediate developer liquid tank, said valve means further comprising a pipe having a longitudinal opening cooperating with said float operated needle valve and secured to said plate, and a horizontally disposed pipe communicating said intermediate developer liquid tank with said longitudinal opening in said pipe. 